Effects of Silodosin on Lower Urinary Tract Symptoms in Patients with Benign Prostatic Hyperplasia: Evaluation by Frequency/Volume Chart

Evolving Role of Silodosin for the Treatment of Urological Disorders – A Narrative Review

Use of α-androgenic receptor blockers remains a mainstay therapeutic approach for the treatment of urological diseases. Silodosin is recommended over other α-blockers for the treatment of lower urinary tract symptoms (LUTS) and benign prostate hyperplasia (BPH), due to its high α_1A uroselectivity. Current research data suggest that silodosin is efficacious in the management of various urological diseases. Thus, we herein review the current evidence of silodosin related to its efficacy and tolerability and appraise the available literature that might ultimately aid in management of various urological conditions at routine clinical practice. Literature reveals that silodosin is beneficial in improving nocturia events related to LUTS/BPH. Silodosin exerts effect on relaxing muscles involved in detrusor obstruction, therefore prolonging the need for patients undergoing invasive surgery. Silodosin treatment, either as a monotherapy or combination, significantly improves International Prostate Symptom Score (IPSS) including both storage and voiding symptoms in patients with BPH/LUTS. Patients on other treatment therapies such as phosphodiesterase 5 inhibitors or other α-blockers are well managed with this drug. Steadily, silodosin has proved beneficial in the treatment of other urological disorders such as chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), overactive bladder/acute urinary retention (AUR), premature ejaculation (PE), and prostate cancer post brachytherapy-induced progression. In patients with distal ureteral stones, silodosin treatment is beneficial in decreasing stone expulsion time without affecting stone expulsion rate or analgesic need. Moreover, there were significant improvements in intravaginal ejaculation latency time, quality of life scores, and decrease in PE profile among patients with PE. Silodosin has also demonstrated promising results in increasing the likelihood of successful trial without catheter in patients with AUR and those taking antihypertensive drugs. Reports from Phase II studies have shown promising role of silodosin in the treatment of CP/CPPS as well as facilitating ureteral stone passage. From the robust data in this review, further silodosin treatment strategies in the management of different urological conditions need to be focused on.

A randomized controlled study of the efficacy of tadalafil monotherapy versus combination of tadalafil and mirabegron for the treatment of persistent overactive bladder symptoms in men presenting with lower urinary tract symptoms (CONTACT Study)

Aim

To evaluate efficacy and safety of combination of tadalafil + mirabegron for overactive bladder/benign prostatic hyperplasia (OAB/BPH).

Methods

Male patients with lower urinary tract symptoms (50 to 89 years), with remaining OAB symptoms even after administering tadalafil for more than 8 weeks were randomly assigned to either tadalafil monotherapy group (5 mg/day) or tadalafil/mirabegron combination therapy group (5 mg/50 mg/day). The primary endpoint was change from baseline in total OAB symptom score (OABSS) at week 12. The secondary endpoints were changes in International Prostate Symptom Score (IPSS), NIH‐chronic prostatitis symptom index (NIH‐CPSI), and micturition chart parameters at weeks 4 and 12.

Results

A total of 176 patients were randomized to either monotherapy (87 patients) or combination therapy (89 patients). The baseline characteristics of patients in the two groups were similar. The total OABSS (95% confidence interval) of combination therapy was significantly decreased by 1.78 (1.05‐2.50) points compared with that of monotherapy (P < .001). Changes from baseline in OABSS nighttime voiding score, urgency score, urgency incontinence score, IPSS storage subscores, NIH‐CPSI total score, and numbers of voids, nighttime‐voids, and urgency episodes/day in micturition chart were significantly reduced in combination therapy (all P < .001). Patient‐reported outcome was significantly more satisfactory in combination therapy than in monotherapy (P < .001). One moderate adverse event (pain in hip joint) with hardly presumed causal relationship with therapy and seven mild adverse events were noted in monotherapy and combination therapy group, respectively.

Conclusions

The effect of tadalafil/mirabegron combination therapy on relieving OAB symptoms appeared to be greater than that of tadalafil monotherapy and can be safely used.

Male lower urinary tract symptoms and α1D-adrenoceptors

Historically, α(1)-adrenoceptors have been classified into three subtypes (α(1)(A), α(1)(B) and α(1)(D)) that are widely distributed in various organs. Research on the α(1)(D)-adrenoceptors in the bladder, urethra and prostate has focused on the relationship between expression levels and symptoms of bladder outlet obstruction, and the implications and functional roles of α(1)(D)-adrenoceptors subtypes in these organs. The α(1)(D)-adrenoceptor messenger ribonucleic acid and protein seem to be increased in obstructed bladders or small capacity bladders. In contrast, α(1)(D)-adrenoceptor subtype knock-out mice have been found to have a prolonged voiding interval. Interestingly, an α(1)(D)-adrenoceptor antagonist was found to inhibit the facilitation of afferent nerve activity for the micturition reflex induced by intravesical infusion of acetic acid. Clinically, patients who felt urgency at low filling volumes and had a small bladder capacity were found to have more α(1)(D)-adrenoceptor messenger ribonucleic acid in their bladder mucosa than patients who felt urgency at high filling volumes and had a large bladder capacity. An α(1)(D)-adrenoceptor antagonist was found to increase the first desired volume and the maximum desired volume while decreasing detrusor overactivity in pressure flow studies. Thus, α(1)(D)-adrenoceptors in the lower urinary tract might play an important role in the pathophysiology of lower urinary tract disorders.